1. Field of the Invention
This invention relates to an improvement of the properties of a polymer containing methacrylimide ring structures (hereinafter referred to as "methacrylimide-containing polymer") having an excellent transparency and heat resistance, and to a blend of this polymer with another thermoplastic polymer.
2. Description of the Related Art
Since a methyl methacrylate polymer has not only an excellent transparency but also satisfactory weatherability and mechanical properties, this polymer is used as a high-performance plastic optical material or a decorative material. Recently, the use of this polymer in the fields of short-distance optical communication and optical sensors has been investigated, but since the heat distortion temperature of the methyl methacrylate polymer is as low as about 100.degree. C, the polymer cannot be satisfactorily applied to fields where a heat resistance is required, and thus an enhancement of the heat resistance is urgently required.
The imidization of a methyl methacrylate polymer is known as a means for improving the heat resistance of this polymer. For example, there have been proposed (1) a process comprising reacting under heating a polymer of acrylic acid, methacrylic acid or an ester thereof with a primary amine, ammonia or a compound capable of generating a primary amine or ammonia in the presence of a solvent (see U.S. Pat. No. 2,146,209, German Patent No. 1,077,872 and German Patent No. 1,242,369), (2) a process comprising reacting a methyl methacrylate polymer with a primary amine in the presence of water (see U.S. Pat. No. 3,284,425), and (3) a process comprising reacting an acrylic polymer with ammonia or a primary amine in an extruder (see U.S. Pat. No. 4,267,374).
The methacrylimide-containing polymers prepared according to these processes, however, have no compatibility or miscibility with many other thermoplastic polymers and thus, when these polymers are blended with other thermoplastic polymers and molded, uniform blends cannot be obtained and the characteristics of the respective polymers cannot be property exerted.
European Patent Publication No. 0216505 proposes that, to improve the compatibility or miscibility of a methacrylimide-containing polymer with other thermoplastic polymers, the amounts of acid and acid anhydride functional groups slightly present on the methacrylimide-containing polymer should be reduced.
In a blend of the methacrylimide-containing polymer obtained according to this proposal with another thermoplastic polymer, however, a substantial improvement of the compatibility and miscibility is not observed, or if an improvement is observed, such an improvement is very slight.